The present invention relates to a load cell type, weight-measuring device in which a distorted beam, which is deformed through receipt of a weight, is converted to an electrical signal to thereby obtain weight data.
In general, in load cells, a zero point voltage (output voltage of a load cell when an effective weight of load is not applied) and a span (differential voltage between the zero point voltage and an output voltage when a rated weight is applied) change when an ambient temperature changes. Therefore, it is necessary to correct the output voltage of the load cell in accordance with temperature change. Temperature compensation for the zero point voltage is executed by interposing a variable resistor (or variable resistors), having particular temperature characteristics, in one side (or two sides) of a bridge circuit having four strain gauges, thereby attaining a bridge balance at substantially any temperature. On one hand, temperature compensation for the span is executed by interposing a variable resistor, having particular temperature characteristics, in the input side of the bridge circuit, thereby changing the input voltage applied to the bridge circuit, in response to the temperature change, and keeping the span constant. On the other hand, to execute temperature compensation for the zero point voltage the interposition of a variable resistor having a predetermined temperature characteristic is required in the bridge circuit, resulting in an increase in the number of manufacturing steps. Also, it is very troublesome to check whether this variable resistor has an accurate resistance value or not. Further, to execute temperature compensation for the span, interposition of a resistor is needed in the input side of the bridge circuit; therefore, the input voltage applied across the bridge circuit decreases as compared with the actual input voltage, causing the rated output voltage to be lowered.